Fluid pump unit



Aug. 19, 1952 MUELLER 2,607,296

FLUID PUMP UNIT Filed May 16, 1946 v 9 Sheets-Sheet 1 Z3 INVENTOR.

BY Herman & f/ue //e r 8'- 1952 H. G. MUELLER 2,607,296

FLUID PUMP UNIT INVENTOR.

Herman 6. Mud

g- 1952 H. G. MUELLER 2,607,296

FLUID PUMP UNIT Filed May 16, 1946 9 Sheets-Sheet 3 IN V EN TOR. y Hrman r/vvvl/er' Aug. 19, 1952 H. G. MUELLER 2,607,296

FLUID PUMP UNIT Filed May 16, 1946 9 Sheets-Sheet 4 V INVENTOR. HMqel/e/ Aug. 19, 1952 H. e. MUELLER 2,607,296

FLUID PUMP UNIT Filed May 16, 1946 v 9 Sheets-Sheet 5 INVENTOR. Her/mm GMeal/87'" BY Aug. 19, 1952 Filed May 16, 1946 H. G. MUELLER FLUID PUMPUNIT 9 Sheets-Sheet 7 Aug. 19, 1952 H. G. MUELLER FLUID PUMP UNIT FiledMay 16. 1946 Q Q Q 9 Sheets-Sheet 8 o ROTAT/O/V CHM A/Vilfj, DEGREES.

IN VEN TOR.

BY Her/n? n 6. Mu e r 7 Aug. 19, 1952 H. G. MUELLER FLUID PUMP UNIT 9Sheets-Sheet 9 Filed May 16, 1946 Patented Aug. 19, 1952 UNITED STATESPATENT OFFICE FLUID PUMP UNIT Herman G. Mueller, Erie,-Pa.

, Application May 16, 1946, Serial No. 670,192

' .2 Claims. 1

This invention relates generally to pumps and more particularly tohydraulic multi-cylinder liquid pumps driven from an external powersource and customarily lifting the liquid to be pumped, by suction, froma sump and forcing it against hydraulic pressure into a discharge line.

Conventional multi-cylinder liquid pumps have 2, 3, or more hydrauliccylinders, either single or double acting, each with a reciprocatingpiston, actuated by a piston rod, a crosshead and a connecting rod,transmitting the rotative'movement from a'crank or eccentric to thereciprocating motion of a crosshead and a piston.

In some cases Scotch yokes are'used with sliding crossheads in the yoke,which are mounted on the crankpin, the crosshead taking one component ofthe rotatingcrank motion and the yoke the other component, they being atright angles to each other. Poppet-type, springloaded suction anddischarge valves are common: 1y used in hydraulic pumps, one or more ofeach generally being provided for each end of each cylinder. v v

The Scotch yoke construction results in a simple harmonic motion of thepiston, and the crank with connecting rod construction, results in asimilar piston motion somewhat modified, due to the angularity of theconnecting rod. With either construction, the piston has its greatestacceleration at the ends of thestroke with the maximum velocity of thepiston and maximum rate of suction or discharge of the liquid near themiddle of the stroke. The lift of the springloaded. valves isapproximately proportional to the piston velocity, or the rate of flowthrough the valves, and it follows that the valve rate of lift or valvevelocity is then approximately proportional .to the piston accelerationwhich, as stated, is maximum at the end of the stroke when the liquidflow is zero and the valve is just beginning to open or is closing. Inother words, the velocity is greatest at the beginning of itsliftyrequiring an impact force to accelerate it instantly from rest, toits maximum velocity. It is also at its maximum velocity, coming to aninstant stop, as it seats. The result is a slamming of the valve inopening and seating and in order that this slamming does not becomeharmful, very slow crank speeds are necessary. Because of these very lowspeeds such pumps are necessarily very large and heavy and costly.

' There are also other reasons necessitatingslow rotative speeds withconventional pumps. Another of these is because of large variations inthe rate of flow of the combined cylinders. With 'suction or intakestroke.

any single reciprocating piston the rate of flow, as stated above, iszero at each end of the stroke. To even out the combined flow,multi-cylinder arrangements are used and in general the more cylindersused the smoother the flow or the smaller the variations in flow.

With a conventional two-cylinder doubleacting connecting rod or Scotchyoke pump and with two cranks in their best relative positions, namelyapart, these flow variations are on the order of twenty-seven per cent(27%) above and below the average with sharp accelerations resulting inenormouspressure pulsations in the discharge line where small pipes andhigh velocity are necessary due to the high pressure In the suctionline, where only atmospheric pressure is used to force the liquidthrough the line, larger pipes are necessary thereby reducing thevelocity and helping to minimize the pressure pulsations. On a dischargeline, dampening air chambers are needed to make operation practical.With a three-cylinder conventional doubleacting pump, these flowvariations reduce to approximately six and one-half per cent (6%%)above, to eighteen and one-half percent (18 /2 below the average flow,but still with sharp accelerations and still requiring air chambers. Dueto these flow variations the lower the number of cylinders, the slowermust be the speed of the pump to keep the resulting pressure variationswithin practical limits.

Another important speed limitation is caused by the necessity of keepingthe piston accelerations down to values low enough to allow the liquidfrom the suction line to follow it on the Where only atmosphericpressure is available in the suction line to provide acceleration of theliquid coming therefrom, which must work against the suction lift andfriction losses through the line and the suction valve, very littlepressure remains from atmospheric pressure on .the suction line foraccelerating the liquid to follow the piston. The result is that theliquid doesnot follow the piston and does not keep the enlargingcylinder entirely filled with liquid and cavitation results in thecylinder and causes very destructive impacts when the piston makes itsreturn stroke. .These impacts frequently wreck the pump and to avoidthem slow speeds are very essential. Where the liquid is heavy andviscous very slow speeds become paramount.

It is accordingly, an. object of my invention to overcome the above andother defects in liquid pumps and it is more particularly an object of 3my invention to provide a liquid pump which is economical in cost,economical in operation, efiicient in operation and economical inmanufacture.

Another object of my invention is to provide a liquid pump whichovercomes the speed limitations heretofore necessary in conventionalliquid pumps and to provide a pump where very much increased speeds maybe used.

Another object of my inventionis to provide a liquid pump which is muchsmaller and lighter than conventional pumps designed for equal orgreater liquid capacity and horsepower.

Another object of my invention is to provide a liquid pump which hasperfectly even suction and discharge line flows byeliminatingallpulsations and using only two double-acting or foursingle-acting cylinders.

used in my novel pump unit.

"Referring now to the drawings, Figures 1 to inclusive, show a crankcase I and a liquid casing 8 mounted on skids 2. Side covers 3 and topcovers 4 are provided on the crank case I for Another object of myinvention is to provide a liquid pump which has a minimum of movingparts. p I

Another object of myjinv'e'ntion is to provide a liquid'pump whichhasia'smoother,valvefajcti on without impacts or slamming of'the valves"and which also permits theuse, of higher valve speeds; Another object ofinvention is to provide ample pressures in the suction] line when thepiston is on,..the suction"strokef using apump for]chieflyaccelerating'the liquid to follow the piston and keep theenlar'gingcylinder entirely full of liquid at higher speeds and toprevent cavitation in the liqu-idcylincler and destructive impacts. H pAnother object or my invention"isfto-"provide in a liquid. pump withfla'minimum 'nuniber oi cy1inders, a continuous smooth now which will resultin smooth and constant torque resistance on the driving shaft .and' thusprevent whipping of the llclrivingv-beltsgflat belts, chains or cou-Another object oinmyjinvention is, to provide a hydraulic pump whichmakes unnecessary the use of heavy fly wheels. I Another object of myinvention is itoeliminja'te sliding orossheads, guide bearings,-oscilla'ting wrist pin bearings, by .using roller bearings throughout,and to fur'ther -eliminate Scotch yokes and connecting rods.

Another object of my invention is to eliminate theconventional largegear and. pinion drive necessitated by the slow rotating speed ofconventional pumps. 1

Another object of my invention is to provide av li'quid pump capable ofhigh enough'.-speeds toeliminate gears for increasing or reducingthevspeeds.

Other objects of my invention will become I evident from thefollowing-detailed description, taken in conjunction with theaccompanying drawings, in which: I I

1' is a side elevationalyiew of anillu'strative embodiment of my novel'fiuid pump' unit, arranged forfbelt drivefrom an engine or a motor anddisposed .on askid for portable use.',.v"

Fig. 2 is an end elevational View, with parts broken away on line l-- -lof Fig. 1 taken from the fluid cylinder end of mynovel 'fluid'pump unit.

Fig. 3 is a plan view, with onerofithecovyers on top of thecasingremove'd.

Fig. 4. is a View taken on the line 2p-Z of .Fig. 5 is a view taken onthe line 33' of Fig. 6 is 'a diagrammatic view showing three curves, twoof these curves representing the norm bined iiow rates throughout onerevolution of conventional pumps, .anfd the third curve"showingready-access to piston rod packing cases 5 and E.

A main cover I is disposed on the top of the crankcase I. Thefluidcasing 8 is disposed longitudinally of the crank case iahdfh9j$i0flhed therein liquid pumping cylindrical portions 9 connectingclosed chambers 1'0 and l' I. Apertures l2 in the casing 8 have seats'i3fior seating inverted conical-shaped valve heads l5, guided by stemsIt.v .Covers I"! have depending cylindrical portions fl8 with coilsprings 19. therea'mu'hd to urge the valve" h'eadsj'lf'il into sealingrelationship with seats l3. Covers llfcl'ose a ertures rain thedischarge chest 2i; in theupp'er part of casing 8; Discharge outlet 22fleadsoutwardl'y from chestZl.

A shaft 129 is 'ournal'ed 'in isleevest and is transverselymountedbelowfthe casing f8 and has fixedly mounted 'thereon'i twoimpellers 3'1; one

with right and the other ,With fleitalian'djvanes.

disposed in annularcasing. I on ppos'ite end of shaft 29 and to increasethe pressure of fiu d entering the inlet line 35jaiitl passing throughsuction chambers '36 and through suction apertures '31 to thechambe'r'sflil and H; Only'the right hand impeller 3| is shown inFig. 2"i-oi" purposes of illustration. Since one impeller right hand vanes andthe other has .left hand vanes, they maybeiexchange'd for rotation in anopposite direction. 'Seats" are disposed in the suction apertures'31 toseat inverted conicalshaped suction valve heads-.41 urged against theseats40 by coil springs 42 surrounding depen ing cylindrical portionsv1Y3 clepehdingjfrom. closing covers 34 disposed over ap'erture's in thecasing'8.

, The suction discharge .v'alve's ar'e o'f the same generalconstruction; One-impeller 3-1 and one booster pump casing 33 isprovided for each pair of suction valves injchambers l 0 arid l Thebooster pump casings '33 are closed by cover-s46 carrying packingfboxes4? with glands 48-. Bearing brackets 38'are bolted to the covers 46 andcarry roller bearings, and sealing rings "50. Shaft 29 is journaled inthe bearings 49 and ex-.

tends outwardly therefrom on both ends thereof-.-

I have shown mounted. on one end of the shaft 29 a fixedly mounted\l-belt pulley 52 secured by nut 53 and I provide a cap '54 to coverthe'extend ing shaft 29 on the opposite end of the shaft '29. Theimpellers 3'! are secured by nuts 39 against the sleeve 30. It willbe'evid'ent that pulley 52 may be used. and mounted'on either end of thshaft 29.

Referring now particularly to Figs. 3, 4, and 5. crank case I has]disposed in the sides thereof. flanged'members' 'for rotatably mountingva transversely" disposed, huh member '61 having longitudinallyextending internal apertures 62 for receiving the tapered ends 63 ofshafts 64. The shafts 64 are oil sealedby'glands II. Reduced ends 65 ofthe hub member 6| engage roller bearings 66carried by the flange members60. Two pair ofieccentric hubs .6! and 68 are cast integral with hubmembers6l, those in each pair being concentric with each other and onepair being spaced 90 from theother. The throw of each eccentric ispreferably made equal to one half the piston stroke. Around eacheccentric is shrunk a hardened and ground cam ring 59.

Engaging each cam ring 59 are two follower roller tires 69, shrunk overand encircling roller bearings 80 mounted on transversely extendedshafts 10 integral with crossheads l2.

Shafts 10 have reduced end portions 13 for engaging roller bearings 14movable with outer tires 90 between longitudinally extending guide-ways15 and 16, the former mounted on pads 11 in the base block 18 of thecasing l and depending ribs 19 forming part of the cover I of the casing7 There are two transversely extending crosshead shafts 10 on each endof each cross-head 12 and there are-also cross-heads about each pair ofcams 59. Each pair of cross-heads 12 are spaced 180 degrees apart aroundthe periphery of the cams 59 with their centers riding in the horizontalplane through the longitudinal center line of the shafts 64. Nuts 55 ateither end of each tie-rod 56 are adjustable to maintain all four camfollowers 6-9 in contact with their respective cams 59 with an initialload and tension thereon. Suitable shims (not shown) or any othersuitable means may be provided for adjustment. Guideways I5 and 16 canbe adjusted vertically with shims in order to adjust the clearancesbetween the upper guide-way l6 and the lower guide-way I5 and-the tires69, so that tires 69 can roll on either the upper or the lowerguide-ways 16 or 15 and clear the opposed guideway. End covers 51 areprovided on the crank case I for access to the nuts 55 securing thetierods 56. After the nuts 55 are removed, the cross-heads 12 can belifted through the top of the crank case byremoving top cover. '1.

The inner ends of the tie-rods 56 extend through apertures in T-shapedcross-head extensions 58 and the latter are secured to the tie-rods 56by nuts 55. The other ends of the extensions 58 are threaded internallyfor threadably engaging the threaded ends of piston rods 5| with nuts8|. Splash plates 82 are secured between nuts 8| and'cross headextensions 58. The extensions 58 are oil sealed by packing boxes 6. Thepiston rods 5| have secured thereto in the cylindrical portions 9 of thecasing 8 conventional piston heads 83 by the internally threaded end 84of extensions 85 of the rods 5| serving as a tail rod of the samediameter as the piston rods 5| in order to give equal displacements offluid from either side of the piston heads 83. On either side of thepiston heads 83 are mounted conventional rubber packings 86 secured withfollower plates 81 and spring rings 88'.

The rubber packings 86 ride on hard liners 89 sealed with a conventionalrubber gasket 9|. The piston rods 5| andthe tail rods 85 pass throughduplicate stufiing'boxes 5 and 92 with conventional duplicate rubberpackings93 and 94 and follower glands 95 and 96. The liners 89 arepressed into the cylindrical portions 9 of the casing 8. It will beevident that the two chambers l0 and II are duplicated in casing 8 andhave duplicate liners, pistons, rods and packing boxes for each cylinderwhose parallel disposition is shown in Figs. 2 and 3.

.A pulley I00 is mounted on the shaft 64 and rotative force istransferred to the pulley 52, mounted on the shaft 29'by V-belts WI. Theshafts 64 are driven from a main power source (not shown) such as a'gasengine, diesel engine, steam engine, or electric motor. If the driverequires two engines, another duplicate pulley 102 shown in dot and dashlines may be mounted on the opposite side of the crank case and maybedriven by additional V-belts. It Will be evident that any form of drivemay be used between shaft 64 mounted in the crank case and shaft 29mounted in the casing 33.

In operation, the shaft 64 is rotatedby a suitable power source, therebyrotating the pulley I00 mounted thereon, to drive the pulley 52on theshaft 29, carrying the impellers 3|. The rota tion of the shafts 64causes the followers 69 'engaging the cam members 59 to reciprocatethereby causing the reciprocation of the piston rods 5|, and the pistons83 attached thereto. The suction and'discharge valves 4| and I5 in thechambers l0 and on each end of the cylindrical portions 9 of the casing8 open and close in accordance with the pressure variations caused bymovement of the pistons 83. There is preferably disposed onesuctionvalve 4| and one discharge valve |5 in each chamber l0 and Hon the endof each cylindrical portion 9 of the casing 8. The fluid entering thesuction valves 4| is placed under pressure by the impellers 3|, tofollow the pistons 83 and to prevent cavitation when they move throughthe enlarging cylindrical portion 9 of the casing 8.

Suction valves 4| are opened by reason of reduced. pressure in thechambers I0 and H and the pressure exerted by the pump impellers 3| re-.ceiving fluid from the inlet line 35. On thedischarge stroke of thepistons 83, the discharge valves l5 are opened by pressure on theirunderside from the pistons 83, which closes the suction valves 4| andthe discharge valves then communicate chambers ID or H to the dischargechest 2| which is open to all four discharge valves l5 and leads to thedischarge line 22.

The theory and advantages in the construction of my novel pump willbecome apparent from a study of the curves in Figs. 6, 7, and 8;

Referring now to Fig. 6, the lowermost curve I90 is the combined rate ofdischarge of two double-acting cylinders with 90 cranks of aconventional pump with the pistons driven by a conventional crank andconnecting rods and without a tail-rod. The base of this curve is scaledwith crank angles for one revolution of 360. degrees, and the verticalscale is the discharge rate in gallons per minute of twin cylinders 6x18 with 2%" piston rods and at revolutions per minute, which is theconventional maximum speed for such a pump handling heavy liquids.

The violent fluctuations in the flow, reach peaks of 26% above to 27%below the average. These exist in both the suction and discharge lines.

This, as stated, is one reason why the speed of' these pulsations. Thevariations are often quite severe and cause much vibration of the linesand connections, and frequently severe liquid hammers are set up, oftencausing ruptures.

. To help smooth out these pulsations, it is customary to increase thenumber of cylinders. The result is illustrated by the middle curve I9IinFig. 6, which shows the combined flow rate of three double-actingcylinders of approximately atotal capacity equal to that of the lowercurve. These three cylinders would be /2 x 12" stroke with 2" rods andwith cranks spaced 120 apart and running at 70 revolutions per minute.The pulsations are somewhat reduced and more equal, but still rise 6above to 18% below the averageflow with sharp accelerations.

With the use of my novel straight line I92 shown inthe uppermost lineinFig. 6 is obtained. This line I92 indicates a constant steady uniformflow without pulsations. This is obtained with only two double-actingcylinders, which in this instance are 6%," x 7", with 2 /4" piston rodsand tailrods. These cylinders, it will be noted, are smaller than eitherof the other two pumps, and the pistons can be run at much higher speeds(in this instance 250 .R. P. M.), giving a much greater flow with a muchsmaller pump.

The reasons for this great advantage will become apparent by examinationof the curves I93, I94, I95, I95, and I97, in Figs. '7 and 8. In each ofthese curves I93, I95, I95, I95, and I9'I, in Figs.

7 and 8, is shown the flow characteristics and thevalve action for onedouble-acting cylinder throughout one revolution. In Fig. 7 is shown thecharacteristics of a conventional cylinder of thecrank and connectingrod type. The lower curves I93, show the flow rate in gallons per minuteon the vertical scale for one crank revolution of 360indicated on thehorizontal scale at tie base. The flow is zero at either end of thestroke when the crank is on dead center, and reaches maximum at nearmid-stroke. The maximum flow in the left lobe is smaller than themaximum flow in the right lobe, due to the piston rod reducing thedisplacement of the former.

It should also be noted that these lobes areno symmetrical about theirvertical axes, which is due to the angularity of the connecting rod. Twoof these cylinders at 90 give the lower curve I99 in Fig. 6, since theyare of the same size and at the same speed. It should also be noted thatthe maximum flow on the left or smaller lobe is equal to the flow at thelowest points in the bottom of'the deepest valleys in the lower curveI90 of'Fig. 6.- This is because the maxima'on these lobes are lower thanthe average combined flow, and'at'these points the other cylinder at 90on the crank is at dead center with zero flow.

' With a conventional Scotch yoke and crank,

V insteadof a, connecting rod and crank, and with tail rod extensionsequal in diameter to the piston rods, the two lobes would be equal andsymmetrical sine curves, which would bring all the valleys to the samelevel on the combined curve,

and at a flow rate of about 400 gallons per min-.

ute.v This, howevenwould still be 18% below the combined averagefiow,and the peaks on a curve similar to curve I9ilin Fig. 6 would be 16%above the average. The general characteristics would remain, althoughthe variations would be somewhat less.

Three curves similar to curves I93 shown in siderations apply,although-the variations are further reduced. Thus, in general, thegreater the number of cylinders, the smoother the combined flow curve. Asmooth curve, however, is only obtained at the expense of a multiplicityof cylinders, and an absolutely straight line is never obtained. Theinherent characteristic of each single cylinder still remains,regardless of the number of cylinders used. v

'We will now consider the valve action on a single conventionalcylinder. :The lower curves I93 in Fig. '7 not only represent the flowin gallons per minute shown by the G. P. M. vertical scale, but also thepiston velocity to another suitable scale and also the valve lift tostill another suitable scale. These valves are similar to those shown inFigs. 2 and 4 and are held against flow by a spring, which means thatthe lift or area of discharge through the valve will be approximatelyproportional to the flow rate of fluid discharge from or to thecylinder. Thus the lower curves I93 in Fig. 7 represent valve lift. Theupper curve I94 in Fig. 7 represents the velocity of valve movement tothe vertical scale shown which, when the valve is rising, is shown abovethe base line, and, when the valve is lowering,

V is shown below the base line. The valve velocity Fig. 7, shows amaximum upward velocity at the beginning of the lift, when the piston ison dead center, and a maximum downward velocity at seating on theopposite dead center. In the case of starting to lift, the valve isaccelerated from a position of rest to-its peak upward velocity,instantly, in nearly zero time, and, conversely, it is decelerated fromits peak downward velocity, instantly, to rest in nearly zero time.These represent very heavy impacts, slamming the valve open and slammingit shut. The value of these impacts is in proportion to the square ofthe crank revolutions per minute, and thus again the speed is limited toavoid severe and destructive valve impacts. This is true of eachcylinder and its valves, regardless of how many cylinders are used inthe interest of smoothing out the combined fiow curve. If a Scotch yokeis used, giving a symmetrical sine flow curve, the same applies, sincethe slope of the sine curve represents valve velocity and the slope ofthe sine curve is proportional to the cosine, which is maximum when thesine is zero. The only difference will be that the starting impacts willbe equal to the seating impacts, and

- Will be the average of the two from a connecting rod pump Where theyare unequal, as shown by the curve I94, in Fig. 7, the greater impactoccurring when the piston is on head end dead center.

In my improved pump, with the pistons operated by properly designedcams, these serious defects are entirely eliminated and thus permit muchhigher speeds, giving not only a constant flow Without pulsations, butalso valve impacts are entirely eliminated.

Referring now to Fig. 8, in, the lower portion, curves I95 represent thehow for one double- .9'-L acting cylinder throughout-Hone revolution inheavy lines, and'curves. I96 the-.flow from the other cylinderat 90'indashed'lines. The chief characteristics of thesecurves arethattheyare symmetrical about vertical cente'rlines at each 90 degreesof cam rotation, and, at the same time, are symmetrical about. a".horizontal centerline at one-half the peak-flows. ,The other impor tantcharacteristic is that the curves. 'Come in tangent to the base line atzeroflow, or, in other words, with zero slope. ,.'Iwo such curves I95and I96 give a combined flow for two double-acting cylinders at 90 aparton the-cam hubs, of. aconstant value, or perfectly smooth ;fiow passingthrough the peak values or peak flows of each single cylinder. In otherwords, one cylinder, when at its peak, maintains the constant averageflow, while the other is on dead center with zero flow. In theparticular curves shown, theflow for each cylinder is equal to K(1-cos;2a.) where K" is a constant function of the stroke and therevolution per minute and. a the cam angle ofrotation from deadcenter.However, any other curves having the above characteristics will serve.

Thus, a perfectly smooth flow is obtained from I and the increment invalve lift divided by'the 1 time used for that increment, the velocityofvalve movement. This, to a suitable scale, is, as before, the slope ofthe flow, or lower curve. This slope, as required above, is zero ateither dead center or at zero flow, so that the valve velocity ofmovement, as shown by the upper curvev I9! is also zero at the beginningof the upward lift and at the end of the downward movement, or atseating. Thus the valve motion lifts and seats with no impacts. The peakvalve velocities are at 45 cam angle instead of at dead center. Thus, mynovel pump can be operated at much higher speeds without valve impacts,and gives a valve action similar to a mechanically operated cam actuatedvalve. In my novel pump the cams actuate the pistons which in turnactuate the valves.

The cams which actuates the pistons, are mounted on an eccentric havinga throw of onehalf the stroke, so that the curvature of the cam is easyand provides only the difference in piston movement derived from theeccentric and that desired to obtain the above characteristics.

Where, as illustrated in Fig. 8, a piston velocity, or flow curve, equalto K (1cos.2a) is used, the piston position at various cam rotationangles will be the integral of this curve, or

sine 2a K awhere a," is the cam rotation angle from dead centerexpressed in radians. From this the shape of the cam is readily derivedby conventional methods.

Fig. 9 shows a cam developed by using the above formulae, namely, pistonvelocity equals formulae, namely, piston velocity equals K (l-cos.2a)and the stroke equals sine2 2a) It will be noted that the peak valvevelocities are at '45? cam angle. It will further be notedthattheeccent'ric BI has a throw equal to one-1 half of the stroke. Thecam 59 is. so designed to give. .flow curves which are symmetrical.about verticallaxes at; each of, rotation and at the same-time aresymmetrical. about a horizontal axis through one-:half, of the peakflows andthe bottom of the curve is tangentto the-baseline. This cam isdesigned to :eliminate valve impacts andto give smooth, constant,.continued flow. .There. is one-other characteristic of liquid pumpswhich limittheir speed,,. and thatlis to accelerate the liquid. on thesuction stroke so. that it will followthe piston and keep the cylinderentirely full of liquid without cavitation. If .this is not insured andcavitation results the piston will receive terriffic impacts when itcloses in on the-liquid on the return stroke. The press'ure'in thesuction line is all that isavailable to accelerate the liquid throughthe line .andpassages and through the suction valve, and'imuststill havesufiicient pressure left to keep accelerating the liquid to the speed ofthe piston- Particularly where heavy viscousliquid are pumped and wherehigh suction lifts are used, the speed of the pump is very limited, withonly atmospheric pres-.- sure on the pump, to supply this acceleration.Even without these limitations, the pump speed is limited, due to thelow pressure of atmosphere on the suction line, and this is furtheraggravated by the sharp variations in the flow of a conventional pump,as already illustrated, requiring sharp accelerations, for whichatmospheric pressure is not sufficient. The cam 59 is preferablydeveloped as shown inFig. 9 by extending radii outwardly from the centerof the shaft 62 at equal angles of 15 degrees, thereby making 24division of the outer circle. The position of the piston at each 15degree rotation of the shaft 62 is determined by utilizing the curvesshown in Fig. 8 with the formula where a is the cam rotation angle fromdead center expressed in radians. By measuring the particular pistonposition on each radii extending outwardly from the center of the shaft62, the pitch line of the cam is found which I have designated as pathof follower center. Arcs are described on each of the radii of the sameradius as the cam followers 69 thereby establishing the necessary pointsto define the outer periphery of the cam 59. The legends shown in Fig. 9are self-explanatory.

These limitations are eliminated in my novel pump by supplying a boosterin the suction line in the form of a centrifugal pump built integralwith the main pump and driven by the main pump drive as illustrated inthe Figs. 1, 2, 3, and 4. The speed of this pump and the impellerdiameter are proportioned to give the necessary pressure at the suctionvalves to accelerate the liquid being pumped, so that it will more thancover the piston acceleration after deducting friction losses and thuskeep the cylinder safely full of liquid at the higher speeds. Since thepiston acceleration is proportional to the square of the pumprevolutions per minute, and since the pressure developed by thecentrifugal pump is also proportional to the square of its revolutionper minute, these will maintain the proper ratio when arranged with adrive as shown in Figs. 1, 2 and 3.

It will be evident from the foregoing that my novel pump unit eliminatesspeed limitations 11 heretofore necessary in conventional pumps, whichprevents cavitation, and which eliminates all large gears and pinionsand other moving parts in conventional pumps. It is further evidentthatI have provided a novel pump which has a smooth constant flow in thesuction and discharge lines, which has a mooth and constant torqueresistance in the cam hubs thereby avoidin}; the usual slipping andvibration occuring where V-belts, chains, and couplings, are used onconventional pumps and one in which speed may be greatly increasedthereby greatly decreasing the size, weight and cost of the pump.

,My novelfluid pump unit may take many different forms such as a, unitwith fluid cylinders on opposite sides of the crankcase, withoutdeparting from the basic design and principles of my invention.

Various changes may be made in the specific embodiment of my inventionwithout departing from the spirit thereof or from the scope of theappended claims.

What I claim is:

1. A fluid pump unit comprising a casing having a reciprocating pumpchamber with cylindri'cal portions in one section thereof, a shaftjournalled in another section thereof, an inlet passageway leading tosaid reciprocating pump chamber and an outlet passagewayleading'therefrom; centrifugal pump chambers having a portion defining apassage'leading to said inlet passageway in said casing, impellers of acentrifugal 12 with said secondshaft, a pulley on said second shaft,means for rotatively engaging said "pulleys, means for rotating said;second mentioned shaft, rods reciprocated by said'cams, pistons operablein the cylindrical portions of saidrrecpirocating pump chamber in saidcasing reciprocated bysaid rods, and suction and discharge valves in theinlet passageway and outlet passageway of said casing, respectively,cooperating with said pistons, said impellers increasing the pressure ofthe fluid entered by said suction valves '2. A fluid pump unit as setforth i-n-claimi wherein said impellers are disposed in said centrifugalpump chambers on opposite ends .of said shaft and they have oppositelydisposed vanes. I HERMAN G. MUELLER.

REFERENCES CITED The followingreferences are of .record in the file ofthis patent:

UNITED STATES PATENTS Talbot Dec. 19, 1944;

